Investors are making big, bearish options bets on high-yield corporate bonds ahead of an expected increase in interest rates from the Federal Reserve.

The idea is that as the Fed begins raising rates, safer assets such as Treasurys will begin yielding more. That means investors won't have to seek out riskier assets like high-yield corporate bonds and junk bonds in order to get returns. With the Fed evaluating when it can start boosting interest rates-and many thinking it will do so by the end of the year- some of those yield trades are already going out of favor.